##### http://autoconf-archive.cryp.to/ax_func_which_gethostbyname_r.html
#
# SYNOPSIS
#
#   AX_FUNC_WHICH_GETHOSTBYNAME_R
#
# DESCRIPTION
#
#   Determines which historical variant of the gethostbyname_r() call
#   (taking three, five, or six arguments) is available on the system
#   and defines one of the following macros accordingly:
#
#     HAVE_FUNC_GETHOSTBYNAME_R_6
#     HAVE_FUNC_GETHOSTBYNAME_R_5
#     HAVE_FUNC_GETHOSTBYNAME_R_3
#
#   If used in conjunction with gethostname.c, the API demonstrated in
#   test.c can be used regardless of which gethostbyname_r() is
#   available. These example files can be found at
#   http://www.csn.ul.ie/~caolan/publink/gethostbyname_r
#
#   based on David Arnold's autoconf suggestion in the threads faq
#
#   Originally named "AC_caolan_FUNC_WHICH_GETHOSTBYNAME_R". Rewritten
#   for Autoconf 2.5x by Daniel Richard G.
#
# LAST MODIFICATION
#
#   2005-01-21
#
# COPYLEFT
#
#   Copyright (c) 2005 Caolan McNamara <caolan@skynet.ie>
#   Copyright (c) 2005 Daniel Richard G. <skunk@iskunk.org>
#
#   This program is free software; you can redistribute it and/or
#   modify it under the terms of the GNU General Public License as
#   published by the Free Software Foundation; either version 2 of the
#   License, or (at your option) any later version.
#
#   This program is distributed in the hope that it will be useful, but
#   WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
#   General Public License for more details.
#
#   You should have received a copy of the GNU General Public License
#   along with this program; if not, write to the Free Software
#   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
#   02111-1307, USA.
#
#   As a special exception, the respective Autoconf Macro's copyright
#   owner gives unlimited permission to copy, distribute and modify the
#   configure scripts that are the output of Autoconf when processing
#   the Macro. You need not follow the terms of the GNU General Public
#   License when using or distributing such scripts, even though
#   portions of the text of the Macro appear in them. The GNU General
#   Public License (GPL) does govern all other use of the material that
#   constitutes the Autoconf Macro.
#
#   This special exception to the GPL applies to versions of the
#   Autoconf Macro released by the Autoconf Macro Archive. When you
#   make and distribute a modified version of the Autoconf Macro, you
#   may extend this special exception to the GPL to apply to your
#   modified version as well.

AC_DEFUN([AX_FUNC_WHICH_GETHOSTBYNAME_R], [

    AC_LANG_PUSH(C)
    AC_MSG_CHECKING([how many arguments gethostbyname_r() takes])

    AC_CACHE_VAL(ac_cv_func_which_gethostbyname_r, [

################################################################

ac_cv_func_which_gethostbyname_r=unknown

#
# ONE ARGUMENT (sanity check)
#

# This should fail, as there is no variant of gethostbyname_r() that takes
# a single argument. If it actually compiles, then we can assume that
# netdb.h is not declaring the function, and the compiler is thereby
# assuming an implicit prototype. In which case, we're out of luck.
#
AC_COMPILE_IFELSE(
    AC_LANG_PROGRAM(
	[[#include <netdb.h>]],
	[[
	    char *name = "www.gnu.org";
	    (void)gethostbyname_r(name) /* ; */
	]]),
    ac_cv_func_which_gethostbyname_r=no)

#
# SIX ARGUMENTS
# (e.g. Linux)
#

if test "$ac_cv_func_which_gethostbyname_r" = "unknown"; then

AC_COMPILE_IFELSE(
    AC_LANG_PROGRAM(
	[[#include <netdb.h>]],
	[[
	    char *name = "www.gnu.org";
	    struct hostent ret, *retp;
	    char buf@<:@1024@:>@;
	    int buflen = 1024;
	    int my_h_errno;
	    (void)gethostbyname_r(name, &ret, buf, buflen, &retp, &my_h_errno) /* ; */
	]]),
    ac_cv_func_which_gethostbyname_r=six)

fi

#
# FIVE ARGUMENTS
# (e.g. Solaris)
#

if test "$ac_cv_func_which_gethostbyname_r" = "unknown"; then

AC_COMPILE_IFELSE(
    AC_LANG_PROGRAM(
	[[#include <netdb.h>]],
	[[
	    char *name = "www.gnu.org";
	    struct hostent ret;
	    char buf@<:@1024@:>@;
	    int buflen = 1024;
	    int my_h_errno;
	    (void)gethostbyname_r(name, &ret, buf, buflen, &my_h_errno) /* ; */
	]]),
    ac_cv_func_which_gethostbyname_r=five)

fi

#
# THREE ARGUMENTS
# (e.g. AIX, HP-UX, Tru64)
#

if test "$ac_cv_func_which_gethostbyname_r" = "unknown"; then

AC_COMPILE_IFELSE(
    AC_LANG_PROGRAM(
	[[#include <netdb.h>]],
	[[
	    char *name = "www.gnu.org";
	    struct hostent ret;
	    struct hostent_data data;
	    (void)gethostbyname_r(name, &ret, &data) /* ; */
	]]),
    ac_cv_func_which_gethostbyname_r=three)

fi

################################################################

]) dnl end AC_CACHE_VAL

case "$ac_cv_func_which_gethostbyname_r" in
    three)
    AC_MSG_RESULT([three])
    AC_DEFINE(HAVE_FUNC_GETHOSTBYNAME_R_3)
    ;;

    five)
    AC_MSG_RESULT([five])
    AC_DEFINE(HAVE_FUNC_GETHOSTBYNAME_R_5)
    ;;

    six)
    AC_MSG_RESULT([six])
    AC_DEFINE(HAVE_FUNC_GETHOSTBYNAME_R_6)
    ;;

    no)
    AC_MSG_RESULT([cannot find function declaration in netdb.h])
    ;;

    unknown)
    AC_MSG_RESULT([can't tell])
    ;;

    *)
    AC_MSG_ERROR([internal error])
    ;;
esac

AC_LANG_POP(C)

]) dnl end AC_DEFUN
